As has been pointed out, it's largely cultural disconnect/unfamiliarity. For example, I feel that I "grew out" of shooters, having started the genre with the original Wolfenstein and the first and then second Doom games, then getting tired when the clones started showing up. I'd be an uninformed ignoramus if I proceed to tar all subsequent FPS type games with the same "tired/cliche/dull" labels I applied to them back when I got tired of the genre - there are plenty of interesting FPS style games around.

Same goes for JRPGs. It doesn't really bother me when people talk negatively about them - do these people actually know of the games they're dismissing, let alone played them to any meaningful extent? More than just the few high profile titles? Yeah, no. Usually whenever I see criticism of JRPGs as a whole I find the speaker to be unsurprisingly uneducated about them. Maybe they had a few unpleasant experiences with unfamiliar mechanics - which is a valid basis for forming an early impression, but no longer holds when they try to apply it as sweeping generalizations against other games they haven't even played. In fact the op made the same mistake, evidenced by that last paragraph there. There are plenty of JRPGs with non-superficial mechanics - you simply haven't come across them.

I enjoy Visual Novels as well - another oft-maligned genre. I've been playing them since the 1990s, and again, I find it easy to dismiss superficial criticism against the genre. People take one look at a few popular examples and then extrapolate it to everything else. If you don't enjoy the core mechanics (they're essentially CYA-type interactive stories, nobody's disputing that), that's fine, everyone has different tastes. Dismissing the content on the other hand is merely ignorance. That wouldn't matter so much if they weren't delivered with such vehemence, as if people liking something they don't is somehow offensive to them. Normally once that kind of argument is bought up in a review or discussion you can already tell the person bringing it up has no idea what he's talking about and is just promoting his own biases.